There is an increasing demand for the use of tamper indicating or pilferproof caps on containers; particularly in the food and beverage industry where tampering with the contents may cause spoilage and inconvenience to the consumer. Plastic caps are widely used on a variety of types of containers. Many attempts have been made at providing pilferproof features on plastic caps to clearly indicate to the consumer whether or not the container has been previously opened. An example of this type of cap is disclosed in Fields, U.S. Pat. No. 3,329,295. The band with tamper indicating feature is snap-fitted over a bead on a threaded container neck. To prevent breakage of the bridges which connect the band to the cap, a specially designed capping chuck is used which grips both the cap and the band at the same time to rotate both parts as the band is snap-fitted over the bead of the container.
Most industries are already set up for screw on type cap applications; however, with the Fields type of closure, special chucks have to be designed which require refitting of many of the existing machines at considerable expense.
Another approach to applying a pilferproof cap to a container involves a downward force to snap-fit not only the band over the bead on the container, but also the threads of the cap over the threads on the container neck. This technique is disclosed in French Pat. No. 1,536,459 to Rapeaud et al. In view of the band being directly snap-fitted over the bead on the container without any twist application, the bridges which connect the band to the cap are not over stressed so that breakage of the bridge is avoided. However, as with Fields, the Rapeaud et al design has the same problem in that substantial modification in the capping machines would be required.
French Pat. No. 1,581,775 to S. A. Albaco, discloses a pilferproof cap having a type of drive system which ensures that the band rotates with the cap, as the band is snap-fitted over a bead on the container. This protects the bridges which connect the band to the tearstrip of the pilferproof arrangement. The drive is provided in the form of closely spaced teeth and notch portions in the pilferproof band and tear part. The teeth and notches abut during cap application to rotate the band with the cap as it is snap-fitted over the container bead. A similar form of drive mechanism is disclosed in the German Offenlegungsschrift No. 1,955,047 to R. Finke. Bridges are used to interconnect the pilferproof band portion to the cap. To protect the bridges, teeth extending downwardly from the cap and upwardly from the band abut one another as the cap is applied to rotate the band with the cap in snapping the pilferproof band over a bead on a container neck. The difficulty with both of these cap designs is that the drive mechanisms are arranged so as to be close to one another or close to the cap and band portions. This results in arrangements which are difficult to mold by injection molding techniques, because narrow spacings between band and cap and the drive devices usually results in "flash" problems where the injected plastic seeps around parts of the mould to undesirably interconnect portions over the narrow spaces.
The pilferproof cap design, according to this invention, provides considerable spacing between all components of band and cap to facilitate injection molding by improved bridge designs for interconnecting the band to cap.